Multi-protocol air conditioner diagnosis circuit

Abstract

The invention relates to the field of air conditioner diagnosis, in particular to a multi-protocol air conditioner diagnosis circuit. Comprising a main control chip, a Bluetooth module circuit, a power supply module circuit, a multi-protocol switching circuit, a home bus circuit and an I2C interface circuit, wherein the multi-protocol switching circuit comprises an interface circuit, a multi-way switch circuit and a change-over switch circuit; the home bus circuit comprises an optical isolation input circuit, a home bus chip circuit and a resistance-capacitance adaptive circuit; the I2C interface circuit is connected with the multi-way switch circuit; the power supply module circuit is connected with the main control chip; and the Bluetooth module circuit is connected with the main control chip. The method is high in compatibility, can diagnose air conditioners of most brands and models, is high in fault recognition accuracy, and improves the maintenance efficiency of the air conditioners. The circuit has a certain anti-interference capability. The air conditioner maintenance device has multiple connection modes such as wired connection and wireless connection, can be connected with multiple host devices such as a mobile phone and a computer, realizes long-distance air conditioner maintenance, and improves the working safety.

Description

Technical Field

[0001] The present invention relates to the field of air-conditioning diagnosis, and in particular to a multi-protocol air-conditioning diagnosis circuit. Background Art

[0002] The wide variety of air conditioner brands and models offers users a wide range of choices. However, this presents a challenge: brand-specific diagnostic equipment is required to diagnose air conditioner problems, as each brand utilizes different communication interfaces and protocols. This requires specialized tools for each brand, and the market lacks a diagnostic tool compatible with all common air conditioner brands. Furthermore, existing air conditioner diagnostic equipment or systems lack online diagnostic capabilities, requiring each repair to be disassembled for diagnosis, which is time-consuming and labor-intensive, hindering the efficiency of air conditioner maintenance. Summary of the Invention

[0003] The purpose of the present invention is to solve the above-mentioned related problems and design a multi-protocol air conditioner diagnostic circuit. To achieve the above-mentioned purpose, the present invention provides the following solutions: A multi-protocol air conditioner diagnostic circuit, comprising: a main control chip, a Bluetooth module circuit, a power module circuit, a multi-protocol switching circuit, a home bus circuit, and an I2C interface circuit; The multi-protocol switching circuit includes an interface circuit, a multi-way switch circuit, and a switching switch circuit; the main control chip is connected to the switching switch circuit, the switching switch circuit is connected to the multi-way switch circuit, the multi-way switch circuit is connected to the interface circuit, and the interface circuit is connected to the air conditioner to be tested; The home bus circuit includes an optical isolation input circuit, a home bus chip circuit, and a resistance-capacitance adaptation circuit. The optical isolation input circuit is connected to the multi-protocol switching circuit, the home bus chip circuit is connected to the optical isolation input circuit, the resistance-capacitance adaptation circuit is connected to the home bus chip circuit, and the resistance-capacitance adaptation circuit is connected to the air conditioner to be tested. The I2C interface circuit is connected to the multi-way switch circuit; The power module circuit is connected to the main control chip.

[0004] As a further improvement of the present technical solution, the multi-protocol air conditioner diagnostic circuit further includes a first serial communication protocol circuit, a second serial communication protocol circuit and an air conditioner LNS communication circuit; The first serial communication protocol circuit, the second serial communication protocol circuit and the air conditioner outdoor unit communication circuit are connected to the main control chip; The first serial communication protocol circuit includes a relay and a common mode filter; The second serial communication protocol circuit includes a common mode filter and a serial communication interface; The air conditioner LNS communication circuit includes a multi-way switch, an optical isolator and a VGA interface.

[0005] As a further improvement of the present technical solution, the switching circuit includes a CD4052B chip U8 and a CD4052B chip U9; The X port of the CD4052B chip U8 is connected to the PC6 port of the main control chip, and the Y port is connected to the PC7 port of the main control chip; the X0~X3 ports are connected to the multi-way switch circuit, and the Y0~Y3 ports are connected to the multi-way switch circuit; The X port of the CD4052B chip U9 is connected to the PC6 port of the main control chip, and the Y port is connected to the PC7 port of the main control chip; the X port is connected in series with a resistor R55 and then connected to a 5V power supply, and the Y port is connected to a 5V power supply through a resistor R56; the X0~X2 ports are connected to the multi-way switch circuit, and the Y0~Y2 ports are connected to the multi-way switch circuit; The INH port of the CD4052B chip U8 is connected in series to the base of the transistor Q7 through a resistor R63; a resistor R65 is connected between the INH port of the CD4052B chip U8 and the resistor R63, the other end of the resistor R65 is grounded, and a resistor R64 is connected in parallel between the transistor Q7 and the resistor R63; the collector of the transistor Q7 is connected to a 5V power supply through a resistor R61; the INH port of the CD4052B chip U9 is connected between the collector of the transistor Q7 and the resistor R61.

[0006] As a further improvement of the technical solution, the multi-way switch circuit includes a ULN2003A chip and relays JD1, JD3, JD4, JD5, JD6, and JD7; The ULN2003A chip is connected to the main control chip, and the ULN2003A chip is connected to the relays JD1, JD3, JD4, JD5, JD6, and JD7; The relays JD1, JD3, JD4 are connected to the CD4052B chip U8; The relays JD5 and JD6 are connected to the CD4052B chip U9.

[0007] As a further improvement of the present technical solution, the I2C interface circuit includes a bridge composed of diodes and resistors; the bridge composed of diodes is connected to the relay JD7, the bridge is connected to 10,000 ohm resistors R49 and R52, the resistors R49 and R52 are connected to the main control chip, and the resistors R49 and R52 are connected to the main control chip through 10,000 ohm resistors R46 and R47 and a 3.3V power supply.

[0008] As a further improvement of the present technical solution, the interface circuit includes a relay JD8, which is connected in parallel with relays JD1, JD3, JD4, JD5, JD6, and JD7, and the air conditioner to be detected is connected to the relay JD8.

[0009] As a further improvement of the present technical solution, the optical isolation input circuit includes a PS9114 chip U13, port 4 of the PS9114 chip U13 is connected to the switching circuit through a resistor R116, port 4 of the PS9114 chip U13 and resistor R116 are connected to port 2 of the PS9114 chip U13 through a resistor R121; port 1 of the PS9114 chip U13 is connected to a 5V power supply through a resistor R113, and port 5 of the PS9114 chip U13 is connected to a 3.3V power supply; port 2 of the PS9114 chip U13 is connected to the home bus chip circuit.

[0010] As a further improvement of the present technical solution, the home bus chip circuit includes a MAX22088 chip U14, wherein port 1 of the MAX22088 chip U14 is connected to the optical isolation input circuit, and port 2 of the MAX22088 chip U14 is connected to the switching circuit; port 11 of the MAX22088 chip U14 is connected to the resistance-capacitance adaptation circuit via a resistor R115; port 7 of the MAX22088 chip U14 is connected to the resistance-capacitance adaptation circuit via a resistor R119. The resistance-capacitance adaptation circuit is connected, and the 12th port of the MAX22088 chip U14 is connected between the 7th port of the MAX22088 chip U14 and the resistor R119 through the resistor R120; the 5V power supply is divided by the resistor R122, the resistor R123 and the resistor R125, and the 22nd port of the MAX22088 chip U14 is connected between the resistor R122 and the resistor R123, and the 21st port of the MAX22088 chip U14 is connected between the resistors R123 and R125.

[0011] As a further improvement of the present technical solution, a diode branch is connected in parallel between the RC adaptation circuit and the home bus chip circuit, the cathode of the first diode of the diode branch is connected to the connecting line between the RC adaptation circuit and the home bus chip circuit, the anode of the second diode is connected to the anode of the first diode, and the cathode of the second diode is grounded.

[0012] As a further improvement of the present technical solution, the resistive-capacitive adaptation circuit includes an RS2105 chip U15; port 3 and port 8 of the RS2105 chip U15 are respectively connected to the home bus chip circuit; the series branch composed of port 2 of the RS2105 chip U15 and capacitor NP1 and the series branch composed of port 5 of the RS2105 chip U15 and capacitor NP2 are connected in parallel; the series branch composed of port 10 of the RS2105 chip U15 and capacitor NP3 and the series branch composed of port 7 of the RS2105 chip U15 and capacitor NP4 are connected in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention; Figure 1 This is a schematic diagram of a multi-protocol air conditioner diagnostic circuit of the present invention; Figure 2 This is a schematic diagram of a switching circuit of a multi-protocol air conditioner diagnostic circuit of the present invention; Figure 3 This is a schematic diagram of a multi-way switch circuit of a multi-protocol air conditioner diagnostic circuit of the present invention; Figure 4 This is a schematic diagram of an I2C interface circuit of a multi-protocol air conditioner diagnostic circuit of the present invention; Figure 5 This is a schematic diagram of a home bus circuit of a multi-protocol air conditioner diagnostic circuit of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a," "an," and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0016] The present invention will be described in detail below with reference to the accompanying drawings.

[0017] Example 1 like Figure 1 As shown, a schematic diagram of a multi-protocol air conditioner diagnostic circuit.

[0018] The circuit is mainly composed of a main control chip, a Bluetooth module circuit, a power module circuit, a multi-protocol switching circuit, a home bus circuit, an I2C interface circuit, a first serial communication protocol circuit, a second serial communication protocol circuit and an air conditioner LNS communication circuit.

[0019] The main control chip uses the STM32F407 microcontroller, an Arm Cortex-M4 core-based microcontroller (MCU) from STMicroelectronics. This high-performance model in the STM32 series is primarily designed for embedded systems requiring fast digital signal processing (DSP), real-time control, and a rich set of peripheral functions. It features a floating-point unit (FPU) and offers processing power of up to 210 DMIPS. It integrates a variety of peripherals and interfaces, including USB On-The-Go High / Frequency Switching (HS / FS), Ethernet, 17 timers, three ADCs, and 15 communication interfaces. It operates at a frequency of 180MHz and features a low-power mode, enabling extended operation.

[0020] The Bluetooth chip module circuit provides a Bluetooth communication interface for the air conditioner diagnostic circuit. In addition to connecting to a computer via traditional wired USB, this circuit can also connect to mobile phones and computers via Bluetooth, greatly facilitating maintenance personnel's use and improving work efficiency.

[0021] The power module circuit provides power to this circuit system.

[0022] The multi-protocol switching circuit comprises an interface circuit, a multi-way switch circuit, and a switching circuit. The main control chip is connected to the switching circuit, which is then connected to the multi-way switch circuit, which is then connected to the interface circuit, which is then connected to the air conditioner under test. The main control chip sends a signal to the switching circuit based on the protocol type of the air conditioner under test. Based on the signal received, the switching circuit switches to the corresponding air conditioner protocol type and communicates with the corresponding signal path of the multi-way switch. The multi-way switch then handshakes with the air conditioner under test through the interface circuit to establish communication. This multi-protocol switching circuit supports switching between multiple communication protocols, including RS485, RS232, TTL, single-line TTL, and UART. The I2C circuit is used to connect to air conditioners that use the I2C protocol. This protocol is a serial communication bus with a multi-master-slave architecture. Therefore, communication with the main control chip is not selected through the switching circuit, but rather directly connects to the air conditioner under test through the path of the multi-way switch circuit.

[0023] The home bus circuit includes an optically isolated input circuit, a home bus chip circuit, and a resistance-capacitance (RC) adapter circuit. This circuit system is used to connect to air conditioners using the home bus communication protocol and communicate with the main control chip through a multi-protocol switching circuit. The optically isolated input circuit is connected to the switching circuit of the multi-protocol switching circuit to isolate interference that may occur during electrical signal transmission. The home bus chip circuit is connected to the optically isolated input circuit and is used to receive and send communication information between air conditioners using the home bus communication protocol. The RC adapter circuit is connected to the home bus chip circuit and to the air conditioner under test. The RC adapter circuit adjusts the optimal circuit parameters based on the specific air conditioner to achieve circuit parameter matching between the circuit and the air conditioner under test, thereby achieving optimal communication efficiency.

[0024] The first serial communication protocol circuit is directly connected to the main control chip and is connected to the air conditioner to be tested through a relay and a common mode filter. The common mode filter uses a two-way chip ACM2012-121-2P-T002.

[0025] The second serial communication protocol circuit is directly connected to the main control chip, passes through two common mode filters ACM2012-121-2P-T002, and is connected to the air conditioner to be tested through the DB9 serial communication interface.

[0026] The air conditioner's LNS communication circuit is directly connected to the main control chip. The main control chip's signal passes through a multiplexer and optical isolator before connecting to the air conditioner under test via a VGA interface. The multiplexer uses the ULN2003A chip, and the optical isolator uses the MOC3023S-TA1 chip.

[0027] Example 2 like Figure 2 As shown, a schematic diagram of a switching circuit of a multi-protocol air conditioner diagnostic circuit.

[0028] The switching circuit includes two CD4052B chips. The X port of CD4052B chip U8 is connected to the PC6 port of the main control chip, and the Y port is connected to the PC7 port of the main control chip. Ports X0 to X3 are connected to the multi-way switching circuit, and ports Y0 to Y3 are connected to the multi-way switching circuit. The X port of CD4052B chip U9 is connected to the PC6 port of the main control chip, and the Y port is connected to the PC7 port of the main control chip. The X port is connected in series with resistor R55 and then connected to a 5V power supply, while the Y port is connected to a 5V power supply through resistor R56. Ports X0 to X2 are connected to the multi-way switching circuit, and ports Y0 to Y2 are connected to the multi-way switching circuit. Ports A and B of CD4052B chip U8, as well as ports A and B of CD4052B chip U9, are all connected to the main control chip to receive data from the main control chip.

[0029] The INH port of the CD4052B chip U8 is connected in series to the base of the transistor Q7 through the resistor R63; a resistor R65 is connected between the INH port of the CD4052B chip U8 and the resistor R63, the other end of the resistor R65 is grounded, and a resistor R64 is connected in parallel between the transistor Q7 and the resistor R63; the collector of the transistor Q7 is connected to the 5V power supply through the resistor R61; the INH port of the CD4052B chip U9 is connected between the collector of the transistor Q7 and the resistor R61.

[0030] CD4052B chips U8 and U9 each select the appropriate circuit based on the data combination received from ports A, B, and INH. Ports X0 and Y0 of CD4052B chip U8 access the RS232 protocol, ports X1 and Y1 access the RS485 protocol, ports X2 and Y2 access the home bus circuit, and ports X3 and Y3 access the UART protocol. Ports X1 and Y1 of CD4052B chip U9 access the TTL protocol and single-line TTL protocol. Data from ports A and B of CD4052B chips U8 and U9 is sent by the main control chip, and the corresponding protocol is selected according to the following table: After selection, the protocol corresponding to the multi-way switch circuit is transmitted to the main control chip through the switching circuit.

[0031] Example 3 like Figure 3 FIG. 1 is a schematic diagram of a multi-way switch circuit of a multi-protocol air conditioner diagnostic circuit.

[0032] The multi-way switch circuit includes a ULN2003A chip and relays JD1, JD3, JD4, JD5, JD6, and JD7; JD1, JD3, JD4, JD5, JD6, and JD7 use UD2-4.5NU relays.

[0033] Ports 1 to 7 of the ULN2003A chip are connected to the main control chip, port 11 of the ULN2003A chip is connected to JD1, serving as the signal transmission path for the RS232 protocol; port 12 of the ULN2003A chip is connected to JD3, serving as the signal transmission path for the RS485 protocol; port 13 of the ULN2003A chip is connected to JD4, serving as the signal transmission path for the UART protocol; port 14 of the ULN2003A chip is connected to JD5, serving as the signal transmission path for the TTL protocol; port 15 of the ULN2003A chip is connected to JD6, serving as the signal transmission path for the single-line TTL protocol; port 16 of the ULN2003A chip is connected to JD7, serving as the signal transmission path for the I2C protocol. Relays JD1, JD3, and JD4 are connected to the CD4052B chip U8 after passing through the protocol circuit; relays JD5 and JD6 are connected to the CD4052B chip U9 after level conversion. Different values ​​of the A, B, and INH ports of the CD4052B chip U8 and the CD4052B chip U9 select corresponding paths. The values ​​of the A, B, and INH ports of the CD4052B chip U8 and the CD4052B chip U9 are controlled by the main control chip, and thus connected to the corresponding multi-way switch circuit.

[0034] Example 4 like Figure 4 FIG. 1 is a schematic diagram of an I2C interface circuit of a multi-protocol air conditioner diagnostic circuit.

[0035] The I2C interface circuit includes a bridge formed by diodes D6-D9. This bridge is connected to relay JD7 in a multi-way switch circuit. The bridge is connected to the main control chip via resistors R49 and R52. Resistors R49 and R52 are connected to the main control chip via resistors R46 and R47 and a 3.3V power supply. The I2C interface connects directly to the air conditioner being tested through the multi-way switch, eliminating the need for a selector switch.

[0036] Example 5 like Figure 5 FIG. 1 is a schematic diagram of a home bus circuit of a multi-protocol air conditioner diagnostic circuit.

[0037] The optically isolated input circuit includes a PS9114 chip U13. Port 4 of the PS9114 chip U13 is connected to a switching circuit via resistor R116. Port 4 of the PS9114 chip U13 and resistor R116 are connected to port 2 of the PS9114 chip U13 via resistor R121. Port 1 of the PS9114 chip U13 is connected to a 5V power supply via resistor R113, and port 5 of the PS9114 chip U13 is connected to a 3.3V power supply. Port 2 of the PS9114 chip U13 is connected to the home bus chip circuit. The optically isolated input circuit effectively converts signal levels and optimizes the integrity of logic signal waveforms.

[0038] The home bus chip circuit includes a MAX22088 chip U14, port 1 of which is connected to the optical isolation input circuit, and port 2 of which is connected to the switching circuit; port 4 of the PS9114 chip U13 of the optical isolation input circuit and port 2 of the MAX22088 chip U14 of the home bus chip circuit constitute a pair of receiving and transmitting ports.

[0039] The 5V power supply is divided by resistors R122, R123, and R125. Port 22 of the MAX22088 chip U14 is connected between resistors R122 and R123, and port 21 is connected between resistors R123 and R125. After voltage division, the voltage at port 22 of the MAX22088 chip is greater than that at port 21, disabling the chip's receiver threshold adjustment function.

[0040] Port 11 of the MAX22088 chip U14 is connected to the RC adaptation circuit via resistor R115, port 7 is connected to the RC adaptation circuit via resistor R119, and port 12 is connected between port 7 and resistor R119 via resistor R120; A diode branch is connected in parallel between the RC adapter circuit and the home bus chip circuit. There are two connecting lines between the RC adapter circuit and the home bus chip circuit, each connected in parallel with a diode branch. The cathode of the first diode in this diode branch is connected to the connecting line between the RC adapter circuit and the home bus chip circuit, the anode of the second diode is connected to the anode of the first diode, and the cathode of the second diode is grounded. These diodes function to clamp the signal level.

[0041] The RC adapter circuit includes the RS2105 chip U15. Ports 3 and 8 of the RS2105 chip U15 are connected to the home bus chip circuit. Port 2 of the RS2105 chip U15 is connected in parallel with capacitor NP1 in series, and port 5 is connected in parallel with capacitor NP2 in series. Port 10 is connected in parallel with capacitor NP3 in series, and port 7 is connected in parallel with capacitor NP4 in series. Because the RC values ​​of NP1-NP4 vary, when connected to an air conditioner, the circuit will select different signal paths based on the brand of the air conditioner to achieve optimal circuit parameters and improve circuit transmission efficiency.

[0042] In summary, the multi-protocol air conditioner diagnostic circuit proposed in this invention boasts strong compatibility and is capable of diagnosing most brands and models of air conditioners on the market. It also accurately identifies faults, significantly improving air conditioner maintenance efficiency. The circuit also exhibits robust anti-interference capabilities and stable operation. Furthermore, the circuit supports multiple connection methods, including wired and wireless, and can be connected to various host devices, such as mobile phones and computers. This allows for remote air conditioner maintenance, making it particularly suitable for air conditioner inspections in high-rise buildings and enhancing operational safety.

Claims

1. A multi-protocol air conditioner diagnostic circuit, characterized in that: include: Main control chip, power module circuit, multi-protocol switching circuit, home bus circuit, I2C interface circuit; The multi-protocol switching circuit includes an interface circuit, a multi-way switch circuit, and a switching switch circuit; the main control chip is connected to the switching switch circuit, the switching switch circuit is connected to the multi-way switch circuit, the multi-way switch circuit is connected to the interface circuit, and the interface circuit is connected to the air conditioner to be tested; The home bus circuit includes an optical isolation input circuit, a home bus chip circuit, and a resistance-capacitance adaptation circuit. The optical isolation input circuit is connected to the multi-protocol switching circuit, the home bus chip circuit is connected to the optical isolation input circuit, the resistance-capacitance adaptation circuit is connected to the home bus chip circuit, and the resistance-capacitance adaptation circuit is connected to the air conditioner to be tested. The I2C interface circuit is connected to the multi-way switch circuit.

2. A multi-protocol air conditioner diagnostic circuit according to claim 1, characterized in that: The multi-protocol air conditioner diagnostic circuit also includes a first serial communication protocol circuit, a second serial communication protocol circuit and an air conditioner LNS communication circuit; The first serial communication protocol circuit, the second serial communication protocol circuit and the air conditioner outdoor unit communication circuit are connected to the main control chip; The first serial communication protocol circuit includes a relay and a common mode filter; The second serial communication protocol circuit includes a common mode filter and a serial communication interface; The air conditioner LNS communication circuit includes a multi-way switch, an optical isolator and a VGA interface.

3. The multi-protocol air conditioner diagnostic circuit according to claim 2, characterized in that: The switching circuit includes a CD4052B chip U8 and a CD4052B chip U9; The X port of the CD4052B chip U8 is connected to the PC6 port of the main control chip, and the Y port is connected to the PC7 port of the main control chip; the X0~X3 ports of the CD4052B chip U8 are connected to the multi-way switch circuit, and the Y0~Y3 ports are connected to the multi-way switch circuit; The X port of the CD4052B chip U9 is connected to the PC6 port of the main control chip, and the Y port is connected to the PC7 port of the main control chip; the X port of the CD4052B chip U9 is connected in series with a resistor R55 and then connected to a 5V power supply, and the Y port is connected to a 5V power supply through a resistor R56; the X0~X2 ports of the CD4052B chip U9 are connected to the multi-way switch circuit, and the Y0~Y2 ports are connected to the multi-way switch circuit; The INH port of the CD4052B chip U8 is connected in series to the base of the transistor Q7 through a resistor R63; a resistor R65 is connected between the INH port of the CD4052B chip U8 and the resistor R63, the other end of the resistor R65 is grounded, and a resistor R64 is connected in parallel between the transistor Q7 and the resistor R63; the collector of the transistor Q7 is connected to a 5V power supply through a resistor R61; the INH port of the CD4052B chip U9 is connected between the collector of the transistor Q7 and the resistor R61.

4. The multi-protocol air conditioner diagnostic circuit according to claim 3, characterized in that: The multi-way switch circuit includes a ULN2003A chip and relays JD1, JD3, JD4, JD5, JD6, and JD7; The ULN2003A chip is connected to the main control chip, and the ULN2003A chip is connected to the relays JD1, JD3, JD4, JD5, JD6, and JD7; The relays JD1, JD3, JD4 are connected to the CD4052B chip U8; The relays JD5 and JD6 are connected to the CD4052B chip U9.

5. The multi-protocol air conditioner diagnostic circuit according to claim 4, characterized in that: The I2C interface circuit includes a bridge composed of diodes and resistors; the bridge composed of diodes is connected to the relay JD7, the bridge is connected to resistors R49 and R52, the resistors R49 and R52 are connected to the main control chip, and the resistors R49 and R52 are connected to the main control chip through resistors R46 and R47 and a 3.3V power supply.

6. The multi-protocol air conditioner diagnostic circuit according to claim 4, characterized in that: The interface circuit includes a relay JD8, which is connected in parallel with relays JD1, JD3, JD4, JD5, JD6, and JD7. The air conditioner to be detected is connected to the relay JD8.

7. The multi-protocol air conditioner diagnostic circuit according to claim 1, characterized in that: The optical isolation input circuit includes a PS9114 chip U13, port 4 of the PS9114 chip U13 is connected to the switching circuit through a resistor R116, port 4 of the PS9114 chip U13 and resistor R116 are connected to port 2 of the PS9114 chip U13 through a resistor R121; port 1 of the PS9114 chip U13 is connected to a 5V power supply through a resistor R113, and port 5 of the PS9114 chip U13 is connected to a 3.3V power supply; port 2 of the PS9114 chip U13 is connected to the home bus chip circuit.

8. The multi-protocol air conditioner diagnostic circuit according to claim 7, characterized in that: The home bus chip circuit includes a MAX22088 chip U14, wherein port 1 of the MAX22088 chip U14 is connected to the optical isolation input circuit, and port 2 of the MAX22088 chip U14 is connected to the switching circuit; port 11 of the MAX22088 chip U14 is connected to the RC adaption circuit via a resistor R115; port 7 of the MAX22088 chip U14 is connected to the RC adaption circuit via a resistor R119. The 12th port of the MAX22088 chip U14 is connected between the 7th port of the MAX22088 chip U14 and the resistor R119 through the resistor R120; the 5V power supply is divided by the resistors R122, R123 and R125, the 22nd port of the MAX22088 chip U14 is connected between the resistors R122 and R123, and the 21st port of the MAX22088 chip U14 is connected between the resistors R123 and R125.

9. The multi-protocol air conditioner diagnostic circuit according to claim 1, characterized in that: A diode branch is connected in parallel between the RC adaptation circuit and the home bus chip circuit, the cathode of the first diode of the diode branch is connected to the connecting line between the RC adaptation circuit and the home bus chip circuit, the anode of the second diode is connected to the anode of the first diode, and the cathode of the second diode is grounded.

10. The multi-protocol air conditioner diagnostic circuit according to claim 1, characterized in that: The resistance-capacitance adaptation circuit includes an RS2105 chip U15; port 3 and port 8 of the RS2105 chip U15 are respectively connected to the home bus chip circuit; the series branch composed of port 2 of the RS2105 chip U15 and capacitor NP1 and the series branch composed of port 5 of the RS2105 chip U15 and capacitor NP2 are connected in parallel; the series branch composed of port 10 of the RS2105 chip U15 and capacitor NP3 and the series branch composed of port 7 of the RS2105 chip U15 and capacitor NP4 are connected in parallel.

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